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1 files changed, 194 insertions, 62 deletions
diff --git a/Documentation/doc-guide/sphinx.rst b/Documentation/doc-guide/sphinx.rst index 02605ee1d876..51c370260f3b 100644 --- a/Documentation/doc-guide/sphinx.rst +++ b/Documentation/doc-guide/sphinx.rst @@ -1,7 +1,8 @@ .. _sphinxdoc: -Introduction -============ +===================================== +Using Sphinx for kernel documentation +===================================== The Linux kernel uses `Sphinx`_ to generate pretty documentation from `reStructuredText`_ files under ``Documentation``. To build the documentation in @@ -27,8 +28,7 @@ Sphinx Install ============== The ReST markups currently used by the Documentation/ files are meant to be -built with ``Sphinx`` version 1.3 or upper. If you're desiring to build -PDF outputs, it is recommended to use version 1.4.6 or upper. +built with ``Sphinx`` version 3.4.3 or higher. There's a script that checks for the Sphinx requirements. Please see :ref:`sphinx-pre-install` for further details. @@ -37,32 +37,19 @@ Most distributions are shipped with Sphinx, but its toolchain is fragile, and it is not uncommon that upgrading it or some other Python packages on your machine would cause the documentation build to break. -A way to get rid of that is to use a different version than the one shipped -on your distributions. In order to do that, it is recommended to install +A way to avoid that is to use a different version than the one shipped +with your distributions. In order to do so, it is recommended to install Sphinx inside a virtual environment, using ``virtualenv-3`` or ``virtualenv``, depending on how your distribution packaged Python 3. -.. note:: - - #) Sphinx versions below 1.5 don't work properly with Python's - docutils version 0.13.1 or upper. So, if you're willing to use - those versions, you should run ``pip install 'docutils==0.12'``. - - #) It is recommended to use the RTD theme for html output. Depending - on the Sphinx version, it should be installed in separate, - with ``pip install sphinx_rtd_theme``. - - #) Some ReST pages contain math expressions. Due to the way Sphinx work, - those expressions are written using LaTeX notation. It needs texlive - installed with amdfonts and amsmath in order to evaluate them. - -In summary, if you want to install Sphinx version 1.4.9, you should do:: +In summary, if you want to install the latest version of Sphinx, you +should do:: - $ virtualenv sphinx_1.4 - $ . sphinx_1.4/bin/activate - (sphinx_1.4) $ pip install -r Documentation/sphinx/requirements.txt + $ virtualenv sphinx_latest + $ . sphinx_latest/bin/activate + (sphinx_latest) $ pip install -r Documentation/sphinx/requirements.txt -After running ``. sphinx_1.4/bin/activate``, the prompt will change, +After running ``. sphinx_latest/bin/activate``, the prompt will change, in order to indicate that you're using the new environment. If you open a new shell, you need to rerun this command to enter again at the virtual environment before building the documentation. @@ -71,8 +58,7 @@ Image output ------------ The kernel documentation build system contains an extension that -handles images on both GraphViz and SVG formats (see -:ref:`sphinx_kfigure`). +handles images in both GraphViz and SVG formats (see :ref:`sphinx_kfigure`). For it to work, you need to install both GraphViz and ImageMagick packages. If those packages are not installed, the build system will @@ -82,7 +68,7 @@ output. PDF and LaTeX builds -------------------- -Such builds are currently supported only with Sphinx versions 1.4 and upper. +Such builds are currently supported only with Sphinx versions 2.4 and higher. For PDF and LaTeX output, you'll also need ``XeLaTeX`` version 3.14159265. @@ -90,26 +76,47 @@ Depending on the distribution, you may also need to install a series of ``texlive`` packages that provide the minimal set of functionalities required for ``XeLaTeX`` to work. +Math Expressions in HTML +------------------------ + +Some ReST pages contain math expressions. Due to the way Sphinx works, +those expressions are written using LaTeX notation. +There are two options for Sphinx to render math expressions in html output. +One is an extension called `imgmath`_ which converts math expressions into +images and embeds them in html pages. +The other is an extension called `mathjax`_ which delegates math rendering +to JavaScript capable web browsers. +The former was the only option for pre-6.1 kernel documentation and it +requires quite a few texlive packages including amsfonts and amsmath among +others. + +Since kernel release 6.1, html pages with math expressions can be built +without installing any texlive packages. See `Choice of Math Renderer`_ for +further info. + +.. _imgmath: https://www.sphinx-doc.org/en/master/usage/extensions/math.html#module-sphinx.ext.imgmath +.. _mathjax: https://www.sphinx-doc.org/en/master/usage/extensions/math.html#module-sphinx.ext.mathjax + .. _sphinx-pre-install: Checking for Sphinx dependencies -------------------------------- -There's a script that automatically check for Sphinx dependencies. If it can +There's a script that automatically checks for Sphinx dependencies. If it can recognize your distribution, it will also give a hint about the install command line options for your distro:: - $ ./scripts/sphinx-pre-install + $ ./tools/docs/sphinx-pre-install Checking if the needed tools for Fedora release 26 (Twenty Six) are available Warning: better to also install "texlive-luatex85". You should run: sudo dnf install -y texlive-luatex85 - /usr/bin/virtualenv sphinx_1.4 - . sphinx_1.4/bin/activate + /usr/bin/virtualenv sphinx_2.4.4 + . sphinx_2.4.4/bin/activate pip install -r Documentation/sphinx/requirements.txt - Can't build as 1 mandatory dependency is missing at ./scripts/sphinx-pre-install line 468. + Can't build as 1 mandatory dependency is missing at ./tools/docs/sphinx-pre-install line 468. By default, it checks all the requirements for both html and PDF, including the requirements for images, math expressions and LaTeX build, and assumes @@ -124,27 +131,105 @@ It supports two optional parameters: ``--no-virtualenv`` Use OS packaging for Sphinx instead of Python virtual environment. +Installing Sphinx Minimal Version +--------------------------------- + +When changing Sphinx build system, it is important to ensure that +the minimal version will still be supported. Nowadays, it is +becoming harder to do that on modern distributions, as it is not +possible to install with Python 3.13 and above. + +Testing with the lowest supported Python version as defined at +Documentation/process/changes.rst can be done by creating +a venv with it with, and install minimal requirements with:: + + /usr/bin/python3.9 -m venv sphinx_min + . sphinx_min/bin/activate + pip install -r Documentation/sphinx/min_requirements.txt + +A more comprehensive test can be done by using: + + tools/docs/test_doc_build.py + +Such script create one Python venv per supported version, +optionally building documentation for a range of Sphinx versions. + Sphinx Build ============ The usual way to generate the documentation is to run ``make htmldocs`` or -``make pdfdocs``. There are also other formats available, see the documentation +``make pdfdocs``. There are also other formats available: see the documentation section of ``make help``. The generated documentation is placed in format-specific subdirectories under ``Documentation/output``. To generate documentation, Sphinx (``sphinx-build``) must obviously be -installed. For prettier HTML output, the Read the Docs Sphinx theme -(``sphinx_rtd_theme``) is used if available. For PDF output you'll also need -``XeLaTeX`` and ``convert(1)`` from ImageMagick (https://www.imagemagick.org). -All of these are widely available and packaged in distributions. +installed. For PDF output you'll also need ``XeLaTeX`` and ``convert(1)`` +from ImageMagick (https://www.imagemagick.org).\ [#ink]_ All of these are +widely available and packaged in distributions. To pass extra options to Sphinx, you can use the ``SPHINXOPTS`` make variable. For example, use ``make SPHINXOPTS=-v htmldocs`` to get more verbose output. +It is also possible to pass an extra DOCS_CSS overlay file, in order to customize +the html layout, by using the ``DOCS_CSS`` make variable. + +By default, the "Alabaster" theme is used to build the HTML documentation; +this theme is bundled with Sphinx and need not be installed separately. +The Sphinx theme can be overridden by using the ``DOCS_THEME`` make variable. + +.. note:: + + Some people might prefer to use the RTD theme for html output. + Depending on the Sphinx version, it should be installed separately, + with ``pip install sphinx_rtd_theme``. + +There is another make variable ``SPHINXDIRS``, which is useful when test +building a subset of documentation. For example, you can build documents +under ``Documentation/doc-guide`` by running +``make SPHINXDIRS=doc-guide htmldocs``. +The documentation section of ``make help`` will show you the list of +subdirectories you can specify. + To remove the generated documentation, run ``make cleandocs``. +.. [#ink] Having ``inkscape(1)`` from Inkscape (https://inkscape.org) + as well would improve the quality of images embedded in PDF + documents, especially for kernel releases 5.18 and later. + +Choice of Math Renderer +----------------------- + +Since kernel release 6.1, mathjax works as a fallback math renderer for +html output.\ [#sph1_8]_ + +Math renderer is chosen depending on available commands as shown below: + +.. table:: Math Renderer Choices for HTML + + ============= ================= ============ + Math renderer Required commands Image format + ============= ================= ============ + imgmath latex, dvipng PNG (raster) + mathjax + ============= ================= ============ + +The choice can be overridden by setting an environment variable +``SPHINX_IMGMATH`` as shown below: + +.. table:: Effect of Setting ``SPHINX_IMGMATH`` + + ====================== ======== + Setting Renderer + ====================== ======== + ``SPHINX_IMGMATH=yes`` imgmath + ``SPHINX_IMGMATH=no`` mathjax + ====================== ======== + +.. [#sph1_8] Fallback of math renderer requires Sphinx >=1.8. + + Writing Documentation ===================== @@ -218,10 +303,10 @@ Here are some specific guidelines for the kernel documentation: examples, etc.), use ``::`` for anything that doesn't really benefit from syntax highlighting, especially short snippets. Use ``.. code-block:: <language>`` for longer code blocks that benefit - from highlighting. + from highlighting. For a short snippet of code embedded in the text, use \`\`. -the C domain +The C domain ------------ The **Sphinx C Domain** (name c) is suited for documentation of C API. E.g. a @@ -242,22 +327,33 @@ The C domain of the kernel-doc has some additional features. E.g. you can The func-name (e.g. ioctl) remains in the output but the ref-name changed from ``ioctl`` to ``VIDIOC_LOG_STATUS``. The index entry for this function is also -changed to ``VIDIOC_LOG_STATUS`` and the function can now referenced by: +changed to ``VIDIOC_LOG_STATUS``. -.. code-block:: rst +Please note that there is no need to use ``c:func:`` to generate cross +references to function documentation. Due to some Sphinx extension magic, +the documentation build system will automatically turn a reference to +``function()`` into a cross reference if an index entry for the given +function name exists. If you see ``c:func:`` use in a kernel document, +please feel free to remove it. - :c:func:`VIDIOC_LOG_STATUS` +Tables +------ +ReStructuredText provides several options for table syntax. Kernel style for +tables is to prefer *simple table* syntax or *grid table* syntax. See the +`reStructuredText user reference for table syntax`_ for more details. + +.. _reStructuredText user reference for table syntax: + https://docutils.sourceforge.io/docs/user/rst/quickref.html#tables list tables ------------ +~~~~~~~~~~~ -We recommend the use of *list table* formats. The *list table* formats are -double-stage lists. Compared to the ASCII-art they might not be as -comfortable for -readers of the text files. Their advantage is that they are easy to -create or modify and that the diff of a modification is much more meaningful, -because it is limited to the modified content. +The list-table formats can be useful for tables that are not easily laid +out in the usual Sphinx ASCII-art formats. These formats are nearly +impossible for readers of the plain-text documents to understand, though, +and should be avoided in the absence of a strong justification for their +use. The ``flat-table`` is a double-stage list similar to the ``list-table`` with some additional features: @@ -301,17 +397,17 @@ and *targets* (e.g. a ref to ``:ref:`last row <last row>``` / :ref:`last row - head col 3 - head col 4 - * - column 1 + * - row 1 - field 1.1 - field 1.2 with autospan - * - column 2 + * - row 2 - field 2.1 - :rspan:`1` :cspan:`1` field 2.2 - 3.3 * .. _`last row`: - - column 3 + - row 3 Rendered as: @@ -323,17 +419,53 @@ Rendered as: - head col 3 - head col 4 - * - column 1 + * - row 1 - field 1.1 - field 1.2 with autospan - * - column 2 + * - row 2 - field 2.1 - :rspan:`1` :cspan:`1` field 2.2 - 3.3 * .. _`last row`: - - column 3 + - row 3 + +Cross-referencing +----------------- + +Cross-referencing from one documentation page to another can be done simply by +writing the path to the document file, no special syntax required. The path can +be either absolute or relative. For absolute paths, start it with +"Documentation/". For example, to cross-reference to this page, all the +following are valid options, depending on the current document's directory (note +that the ``.rst`` extension is required):: + + See Documentation/doc-guide/sphinx.rst. This always works. + Take a look at sphinx.rst, which is at this same directory. + Read ../sphinx.rst, which is one directory above. + +If you want the link to have a different rendered text other than the document's +title, you need to use Sphinx's ``doc`` role. For example:: + + See :doc:`my custom link text for document sphinx <sphinx>`. + +For most use cases, the former is preferred, as it is cleaner and more suited +for people reading the source files. If you come across a ``:doc:`` usage that +isn't adding any value, please feel free to convert it to just the document +path. + +For information on cross-referencing to kernel-doc functions or types, see +Documentation/doc-guide/kernel-doc.rst. + +Referencing commits +~~~~~~~~~~~~~~~~~~~ + +References to git commits are automatically hyperlinked given that they are +written in one of these formats:: + + commit 72bf4f1767f0 + commit 72bf4f1767f0 ("net: do not leave an empty skb in write queue") .. _sphinx_kfigure: @@ -342,7 +474,7 @@ Figures & Images If you want to add an image, you should use the ``kernel-figure`` and ``kernel-image`` directives. E.g. to insert a figure with a scalable -image format use SVG (:ref:`svg_image_example`):: +image format, use SVG (:ref:`svg_image_example`):: .. kernel-figure:: svg_image.svg :alt: simple SVG image @@ -356,7 +488,7 @@ image format use SVG (:ref:`svg_image_example`):: SVG image example -The kernel figure (and image) directive support **DOT** formated files, see +The kernel figure (and image) directive supports **DOT** formatted files, see * DOT: http://graphviz.org/pdf/dotguide.pdf * Graphviz: http://www.graphviz.org/content/dot-language @@ -375,7 +507,7 @@ A simple example (:ref:`hello_dot_file`):: DOT's hello world example -Embed *render* markups (or languages) like Graphviz's **DOT** is provided by the +Embedded *render* markups (or languages) like Graphviz's **DOT** are provided by the ``kernel-render`` directives.:: .. kernel-render:: DOT @@ -387,7 +519,7 @@ Embed *render* markups (or languages) like Graphviz's **DOT** is provided by the } How this will be rendered depends on the installed tools. If Graphviz is -installed, you will see an vector image. If not the raw markup is inserted as +installed, you will see a vector image. If not, the raw markup is inserted as *literal-block* (:ref:`hello_dot_render`). .. _hello_dot_render: @@ -402,8 +534,8 @@ installed, you will see an vector image. If not the raw markup is inserted as The *render* directive has all the options known from the *figure* directive, plus option ``caption``. If ``caption`` has a value, a *figure* node is -inserted. If not, a *image* node is inserted. A ``caption`` is also needed, if -you want to refer it (:ref:`hello_svg_render`). +inserted. If not, an *image* node is inserted. A ``caption`` is also needed, if +you want to refer to it (:ref:`hello_svg_render`). Embedded **SVG**:: |